We need an united European train fares and reservation system already.
Just idly checking train prices:
Barcelona-Paris, 20th October, 10:05-16:50: 29 euro on RENFE website. The very same train: 122 euro on SNCF website.
WTF.
(Munchen-Hamburg, which has a similar route length: 18 euro, or 13.40 with BahnCard 25)
(Also that means that Barcelona-Berlin is doable via Paris/Frankfurt in 21 hour and 70 euro, but not the other way around)